SEASONAL DIFFERENCES IN AIRWAY HYPERRESPONSIVENESS IN ASTHMATIC-PATIENTS - RELATIONSHIP WITH ALLERGEN EXPOSURE AND SENSITIZATION TO HOUSE-DUST MITES

Background The degree of airway hyperresponsiveness in allergic asthma tic patients may be influenced by changes in environmental exposure to inhalant allergens. Objective This study investigates the relationshi p between seasonal changes in exposure to house dust mite (HDM) allerg ens and non-specific airway hyperresponsiveness in asthmatic patients with multiple sensitizations to inhaled allergens. Methods In 43 asthm atic patients sensitized to several inhalant allergens, lung function (FEV1), airway hyperresponsiveness (PC20 histamine), serum total IgE, house dust mite (HDM) specific IgE and number of peripheral blood eosi nophils were measured during autumn 1990 (September-November) and spri ng 1991 (March-May). During each season, floor dust samples were colle cted twice from living- and bedrooms and the concentration of the HDM allergens Der p 1 and Der p 2 determined. Results More severe airway h yperresponsiveness (lower PC20 histamine) during autumn was only found in patients sensitized to HDM (n = 32; autumn: 2.05 mg/mL, spring: 4. 51 mg/mL (geometric means), P<0.01), whereas in patients not sensitize d to HDM (n = II) similar values were observed in both seasons (3.44 a nd 4.52 mg/mL, respectively, P = 0.56). More severe airway hyperrespon siveness of HDM sensitized patients in autumn was significantly associ ated with higher Der p 1 concentrations in floor dust. Aside from airw ay hyperresponsiveness, seasonal changes in serum total IgE and number of peripheral blood eosinophils were seen in patients sensitized to H DM. Conclusions In allergic asthmatic patients, airway hyperresponsive ness may increase during autumn, depending on sensitization to HDM and an increase of exposure to HDM allergen.